Last week, Russia launched a first-ever salvo of four intercontinental, nuclear capable submarine launched ballistic missile in under 15 seconds from a single submarine. Many pointed to this capability demonstration as more than just a test of their newest sub platform and accompanying missiles — they saw it as a demonstration of Russia’s growing emphasis on submersible naval warfare.

The same week, U.K. Defense Secretary Gavin Williamson spoke before a crowd at the Royal United Service Institute’s conference on sea warfare, offering a sobering glimpse into just how widespread Russian submarine and general naval activity has become in the waters around the United Kingdom.

“Look at Russia’s resurgence under President Putin. Its submarine activity has increased tenfold in the North Atlantic,” he said. “But that’s not all — in 2010 a Royal Navy ship was called on just once to respond to Russian Navy ships approaching UK territorial waters. Last year we had to respond 33 times.”

Williamson went on to assert that this dramatic uptick in Russian naval activity “goes to show the increasing aggression, increasing assertiveness of Russia.”

The U.K. isn’t the only nation that has recently taken notice of Russia’s resurgent emphasis on submarine warfare. Aside from conventional concerns about Russia’s work to bolster their Baltic and Northern fleets, this year’s nuclear posture review confirmed that the Defense Department believes Russia’s long touted “Ocean Multipurpose System Status-6, or “Kanyon” to the Pentagon, actually exists. The nearly 80 foot long drone submersible is not only stealthy, but it houses a massive 100 megaton nuclear weapon that could decimate a coastal city and produce an irradiated tidal wave that would greatly increase the scope of the weapon’s destructive capabilities. Some defense experts have even gone so far as to call the Status-6 a “doomsday” weapon — as it’s nuclear payload is twice that of the largest nuclear detonation ever in history.

The U.S. has recently begun multiple initiatives aimed at identifying encroaching Russian submarines and engaging them if necessary. DARPA’s PALS project tracks the behavior of marine wildlife, hoping dispersed undersea animals can indicate the presence of a submarine’s electromagnetic field, and the U.S. Navy recently took receipt of their first Sea Hunter Anti-Submarine Warfare Continuous Trail Unmanned Vessel, or ACTUV — a 132 foot long, 140 ton drone warship designed specifically to root out hidden subs.

Perhaps most telling, the U.S. Navy recently made the decision to bring back its mothballed Second Fleet. The Second Fleet is tasked with policing the North Atlantic and America’s East Coast, and officials didn’t dance around the subject. The justification for the return of the Second Fleet was clear: to counter Russian aggression.

Russian submarines are prowling the Atlantic, testing our defenses, confronting our command of the seas, and preparing the complex underwater battlespace to give them an edge in any future conflict,” Naval Forces Europe commander Adm. James Foggo III wrote in the U.S. Naval Institute’s publication, Proceedings. “Not only have Russia’s actions and capabilities increased in alarming and confrontational ways, its national-security policy is aimed at challenging the United States and its NATO allies and partners.”

These endeavors may be coming too slowly, however, as Russia recently announced that it had successfully sent an unknown number of Akula-class Shchuka-B nuclear-powered attack submarines to American coasts, parked them outside Naval bases, and then made their way back all without detection. The American Defense Department has opted not to address Russia’s claims, though the Kremlin recently announced a state-funded docudrama series based on the exercise is entering production.

Featured image: A Russian nuclear submarine, Yuri Dolgoruky, is seen during sea trials near Arkhangelsk, Russia. The submarine was commissioned by the Russian Navy on Thursday, Jan. 10, 2013 | AP Photo/Alexander Zemlianichenko